The present disclosure relates to semiconductor integrated circuits having a first and a second IO cell region, in each of which one or more IO cells into and from a signal having a first voltage amplitude is input and output are formed.
Japanese Patent Publication No. 2000-21987 describes a semiconductor device in which an internal logic circuit region is doubly surrounded by two sets of IO cells arranged in a square ring (in other words, the IO cells are arranged in two square rings (a double square ring) around the internal logic circuit region).
In recent years, as microfabrication technology has been advanced, the breakdown voltages of elements formed on semiconductor integrated circuits have decreased. Therefore, in order to maintain the reliability of the elements, voltages used in the internal circuits of semiconductor integrated circuits tends to be lowered. On the other hand, in systems, such as electronic devices etc., voltages having conventional levels are still used in parts outside the internal circuit (hereinafter referred to as “external parts”). Therefore, the voltages of signals transmitted to and received from the external parts have levels different from those of voltages used in the internal circuit.
Therefore, it is contemplated that a level shift circuit may be provided in an IO cell, and a high-voltage signal transmitted to and received from the external parts is converted into a low-voltage signal suitable for the internal circuit using the level shift circuit in the IO cell. However, if such IO cells are arranged in two lines (double line) in a peripheral portion of the semiconductor integrated circuit (i.e., one (inner line) of the two lines is surrounded by the other line (outer line)), a low-voltage signal transferred between the outer IO cell and the internal circuit passes through a region of the inner IO cell where a high-voltage signal is used, and therefore, is affected by crosstalk caused by the high-voltage signal. As a result, noise occurs in a signal input from the outer IO cell to the internal circuit. Similarly, a low-voltage signal output from the internal circuit toward the outer IO cell passes through the region of the inner IO cell where a high-voltage signal is used, and therefore, is affected by crosstalk caused by the high-voltage signal. As a result, noise occurs in a signal output from the internal circuit to the outer IO cell. In particular, in state-of-the-art microfabrication technology, the voltage of external parts is three or more times as high as the voltage of the internal circuit, and therefore, noise caused by crosstalk further increases, there is a possibility that a signal is not correctly transferred.